A number of well intervention applications are required when completing wells with formation isolation valves. Such valves are typically installed during completion operations and mechanically closed to prevent fluid loss when tubing and/or other tools are pulled through them. The valves may be re-opened remotely by applying a sequence of pressure pulses. However, in a subset of installations, ranging between about five percent and about ten percent, the valve opening mechanism may become stuck, requiring the valve to be shifted mechanically via a downhole tool.
A stuck valve may be mechanically shifted using coiled tubing. The coiled tubing may be used to clean out well debris and residual fracturing sand or particles prior to shifting the valve. However, the cost, footprint, and operational time required for deployment of a coiled tubing unit and other related equipment makes this option undesirable.
Accordingly, mechanical valve shifting operations may be performed using a downhole stroker tool run via a wireline. Prior to running the stroker tool, a clean-up run is often conducted utilizing a milling tool fitted with a brush bit and assisted with a debris collection tool. Although mechanical valve shifting is often successfully accomplished with the stroker tool, the push/pull forces generated by stroker tools are limited. For example, a 2⅛ inch stroker tool may generate a maximum push/pull force of about 12,000 pounds. Other stroker tools may generate about 24,000 pounds of force. Often times, however, static friction caused by sand or other contaminants may prevent the formation isolation valve, or another downhole valve or tool installed within the wellbore, from shifting or being dislodged with the stroker tool. Under such conditions, push/pull forces exceeding operational limits of the stroker tools are necessary to shift the valves or other downhole tools that are stuck.